A single wheel caster of this general type is known for example from DE 20 2011 005 192 U1 co-owned by applicant.
Casters of this type and other types are typically completely mounted in a factory and then have to be attached at a later point in time at hospital beds, medical equipment of similar. When mounting a completely delivered caster there are problems over and over again in practical applications where an installation space between wheel and support element for arranging attachment bolts is very small so that it is even difficult and time consuming with specially adapted tooling to attach the complete caster at a rolling frame or similar. This generated the idea to sell casters in a kit.